JP4895171B2 - Composite core and reactor - Google Patents

Description

  The present invention relates to a reactor composite magnetic core used in a power supply circuit that drives a high output electric motor of a hybrid vehicle, and a reactor.

  The magnetic core of the power circuit reactor can be roughly divided into three. In the region of several tens of kHz or less, silicon steel plates, amorphous soft magnetic strips, microcrystalline soft magnetic strips, etc. are mainly used as magnetic core materials. These magnetic core materials are mainly composed of iron and have the advantages of large saturation magnetic flux density Bs and magnetic permeability μ, but silicon steel plates have the disadvantage of high frequency magnetic core loss. The crystalline soft magnetic strip has a defect that its magnetic core shape is restricted to a wound magnetic core shape or a laminated magnetic core shape and is difficult to be formed into various shapes like ferrite described later.

  In the region of several tens of kHz or more, ferrite cores typified by Mn-Zn and Ni-Zn are widely used. Since this ferrite core has a small high-frequency core loss and is relatively easy to mold, it has the feature that various shapes can be mass-produced. However, since the saturation magnetic flux density Bs is only about one-third to one-half that of the aforementioned silicon steel plate, amorphous soft magnetic strip, and microcrystalline soft magnetic strip, magnetic saturation is not achieved in the high current reactor. In order to avoid this, there is a disadvantage that the magnetic core cross-sectional area becomes large.

  There is a dust core as a magnetic core for a reactor used in a region from several kHz to several hundred kHz. The dust core is formed by subjecting the surface of the magnetic powder to insulation treatment and then processing, and generation of eddy current loss is suppressed by the insulation treatment. However, the high frequency magnetic core loss is larger than that of a ferrite material, an amorphous soft magnetic strip, and a microcrystalline soft magnetic strip.

  Recently, a hybrid vehicle that has begun to spread rapidly has a high-output electric motor, and a power circuit for driving the motor uses a reactor that can withstand a high voltage and a large current. There is a strong demand for miniaturization, low noise and low loss in this reactor, and the magnetic properties of the magnetic core material used in the reactor are required to have a high saturation magnetic flux density Bs and an appropriate range of permeability μr. The appropriate range of permeability μr here will be described below. The magnetic field H and the magnetic flux density B have a relationship of B = μoμrH. Here, μo represents the magnetic permeability in vacuum, and the magnetic field H is proportional to the current flowing through the reactor. For this reason, in a magnetic core material having a high magnetic permeability, even when a small reactor current is reached, the saturation magnetic flux density Bs is reached and the magnetic core is saturated. Therefore, conventionally, a magnetic material with a high saturation magnetic flux density Bs is used as the reactor magnetic core material, and a gap is provided in this magnetic core material to reduce the effective magnetic permeability (effective magnetic permeability) μre, which is necessary by adjusting the number of windings. Designed to obtain a good inductance. The practical effective permeability μre for this application is in the range of approximately 5 to 50.

  A magnetic material having a high saturation magnetic flux density Bs and a low coercive force is used for the reactor core for high current. In general, a magnetic material having a low coercive force also has a high magnetic permeability, and therefore, when used in a reactor magnetic core, a magnetic gap (gap) is provided. The magnetic permeability of the member constituting this gap is about 1. However, in the portion where the gap is provided, a fringing magnetic flux is generated in which the magnetic flux leaks outside the magnetic path. When this fringing magnetic flux passes through the coil, there is a problem that eddy current is generated in the coil and the reactor loss is greatly increased.

  In order to prevent an increase in reactor loss due to the fringing magnetic flux, Patent Document 1 describes changing the laminating direction of the electromagnetic steel sheets radially. However, Patent Document 1 relates to a reactor and a transformer using a unidirectional electrical steel sheet used at a commercial frequency such as 50 Hz, and a magnetic core and a reactor used in a power circuit having a drive frequency of 1 kHz or more according to the present invention. Are different objects.

  Moreover, as a reactor core for large currents, there is one using the above-described dust core. Since the magnetic permeability of the dust core is about 10 to 150, the gap can be reduced as compared with the soft magnetic strip. On the other hand, since the magnetic permeability is low in the entire magnetic path, a fringing magnetic flux is easily generated. For this reason, since an eddy current arises in a coil, there exists a problem that a reactor loss becomes large. In addition, the material used as the powder magnetic core has a high magnetic core loss at a high frequency as compared with the amorphous soft magnetic ribbon and the microcrystalline soft magnetic ribbon. In addition, there is a disadvantage that the difference between the initial permeability and the high-current permeability is large and the current characteristic of the inductance is poor.

Moreover, patent document 2 is disclosed as a reactor which combined both high-permeability members, such as an electromagnetic steel plate, and low-permeability members, such as a dust core. In Patent Document 2, an annular oval reactor is disclosed, and in the embodiment, a leg iron core formed from a laminated steel plate in a rectangular planar shape, and arranged close to the leg iron core to close the magnetic path of the leg iron core. A semi-annular yoke iron core is disclosed. Furthermore, it is described that the yoke core may be a dust core integrated type.
JP 2004-186450 A ((0034) to (0045), FIG. 1) JP 2003-45724 A ((0021), (0024), FIG. 1)

Patent Document 2 discloses a reactor that combines a high-permeability member and a low-permeability member such as a dust core, but it merely describes a rough configuration as an embodiment, It does not completely satisfy the required reactor loss and inductance current characteristics, and there is room for further study.
An object of the present invention is to solve the above-described problems of the conventional high-current reactor core, to improve the current characteristics of the inductance, and to suppress the increase in the reactor loss due to the fringing magnetic flux of the gap. And to provide a reactor.

The present invention is an annular composite magnetic core, wherein the composite magnetic core includes a first and second straight magnetic paths in which a plurality of magnetic core portions are arranged in a straight line, and the first and second straight lines. A first corner portion disposed on one end side of the magnetic path and a second corner portion disposed on the other end side, wherein the first and second corner portions have a maximum relative magnetic permeability of 500 or more. Of the first and second linear magnetic paths and a gap, and the first and second linear magnetic paths have a maximum relative permeability of 500 or more. A magnetic core portion having a high magnetic permeability is used at both ends, and a plurality of magnetic core portions made of a green compact having a maximum relative permeability of 200 or less are arranged between the magnetic core portions at both ends. The magnetic cores arranged in the two linear magnetic paths are arranged via gaps. And wherein the Rukoto.

For the first and second corner portions, a laminate of an amorphous soft magnetic strip or a microcrystalline soft magnetic strip can be used.

The first and second corner portions may be semicircular.

As the green compact, iron-silicon alloy powder, iron-silicon-aluminum alloy powder, amorphous soft magnetic powder, or microcrystalline soft magnetic powder can be used.

The composite magnetic core of the present invention is characterized in that the inductance when measured at a DC current of 160 A and a frequency of 10 kHz is 220 μH or more, and the inductance when measured at a DC current of 330 A and a frequency of 10 kHz is 60 μH or more. Further, the inductance when measured at a direct current of 0 A and a frequency of 10 kHz can be 250 to 300 μH.

The composite magnetic core of the present invention can have a reactor loss of 45 W or less when a ripple current having an effective value of 11.5 A is passed at a frequency of 10 kHz.

In the present invention, the composite magnetic core is wound, and the coil is arranged so as to cover all the gaps between the corner portion and the linear magnetic path and the gaps between the magnetic core portions of the linear magnetic path. It is used as a reactor that has been made.

In the reactor of the present invention, a high permeability magnetic core portion made of an amorphous soft magnetic strip or a microcrystalline soft magnetic strip, a powder magnetic core portion formed by mixing magnetic powder, an insulating material, and a binder, and By using a composite magnetic core composed of gaps provided between the high magnetic permeability magnetic core parts and the dust core parts, the saturation magnetic flux density as a whole of the magnetic core is high, and the magnetic permeability is reduced with respect to DC superposition. It becomes possible to manufacture a small reactor.
Further, in the present invention, since there is a dust core, the ratio of the gap to the magnetic path length is low, and the gap is provided between the high permeability core and the dust core, so the energy of the magnetic flux Is once relaxed in the gap of the high magnetic permeability core portion, the fringing leakage magnetic flux in the gap adjacent to the dust core portion is reduced. Thereby, the leakage magnetic flux which penetrates into the coil is reduced, and the reactor loss is suppressed to a value as small as possible.
If a gap is not provided between the high magnetic permeability cores, the reactor loss will increase. This is because when the magnetic flux enters the dust core from the high magnetic permeability core, the energy of the magnetic flux does not fully correspond to the difference in magnetic resistance between the high permeability core and the dust core, and is adjacent to the dust core. It is presumed that the fringing leakage magnetic flux becomes larger due to the gap. This leakage magnetic flux enters the coil, increasing the loss.

The composite magnetic core of the present invention is particularly suitable for a high current reactor used in a power supply circuit of 20 A or more. It is preferable that the ratio of the powder magnetic core part in the total magnetic path length is 20 to 60%. This is because if the ratio is 20% or more, the gap length becomes small and the reactor loss due to the fringing magnetic flux becomes smaller. If this ratio is less than 60%, the difference between the initial permeability and the permeability at the time of a large current is reduced, and the current characteristics of the inductance are improved. For a large current reactor, the total magnetic path length is preferably 150 mm to 350 mm. Further, the magnetic path cross-sectional area of the high-permeability magnetic core portion and a dust core portion is preferably a 500mm ² ~1000mm ^2.

  In the present invention, the gap includes a portion having a magnetic permeability equivalent to that of the air gap, and may be not only an air gap but also a plate-like member made of a nonmagnetic material such as a resin. Positioning can be easily performed by this plate-like member.

The composite magnetic core of the present invention has a substantially oval shape, a corner portion having a curvature composed of the high magnetic permeability magnetic core portion, the high magnetic permeability magnetic core portion disposed through a gap from the corner portion, and the dust core. And a linear straight portion composed of a gap formed between the dust core portions, it is possible to design a reactor having a small dimensional shape while being for a large current reactor. For a high current reactor, the corner portion preferably has a semi-annular shape with a radius of 10 mm to 30 mm. The entire straight portion is preferably 50 mm to 150 mm.
Moreover, it is preferable that a gap is formed between the high permeability magnetic core portion and the dust core portion in the straight portion. The reactor loss due to the fringing magnetic flux can be further reduced.

  The above-described composite magnetic core of the present invention has an inductance when measured at a DC current of 160 A and a frequency of 10 kHz is 220 μH or more, and an inductance when measured at a DC current of 330 A and a frequency of 10 kHz is 60 μH or more. Can be obtained. The inductance when measured at a direct current of 0 A and a frequency of 10 kHz is 250 to 300 μH.

  Further, the composite magnetic core of the present invention has a reactor energy loss of 40 W or less when a ripple current having an effective value of 11.5 A is flowed at a frequency of 10 kHz, and an unprecedented high characteristic reactor can be obtained.

  In the present invention, an unprecedented high-performance reactor can be obtained by providing coils in these composite magnetic cores. In order to prevent the fringing magnetic flux from affecting the external circuit, it is preferable to design a shape in which the periphery of the gap is covered with a coil.

As an amorphous soft magnetic strip used in the high permeability core of the present invention, the alloy composition is Fe _a Si _b B _c C _d M ′ _α (atomic%) (where M ′ is Cr, Mo, Zr, Hf And at least one element selected from the group consisting of Nb, 76 ≦ a ≦ 84%, 0 <b ≦ 30%, 0 <c ≦ 25%, 0 ≦ d ≦ 3%, 0 ≦ α ≦ 5 Amorphous soft magnetic strips with a content of at least 0.5% or less of Mn, S, P, Sn, Cu, Al, Ti, as unavoidable impurities may be used. For example, an iron-based amorphous soft magnetic material 2605SA1 manufactured by Metglas, USA can be used.
Further, as a fine crystalline soft magnetic strip, the general _{formula: Fe 100-x-y-} z-α-β-γ Cu x Si y B z M 'α M "β X γ ( atomic%) (wherein, M ′ Is at least one element selected from the group consisting of Nb, W, Ta, Zr, Hf, Ti and Mo, M ″ is V, Cr, Mn, Al, a white metal element, Sc, Y, Au, Zn , Sn, Re, at least one element selected from the group consisting of X, X is at least one element selected from the group consisting of C, P, Ge, Ga, Sb, In, Be, As, and x , y, z, α, β, and γ are 0.1 ≦ x ≦ 3, 0 <y ≦ 30, 0 <z ≦ 25, 5 ≦ y + z ≦ 30, 0.1 ≦ α ≦ 30, 0 ≦ β ≦ 10 and 0, respectively. ≦ γ ≦ 10.) Fe-based alloy in which at least 50% of the structure is composed of fine crystal grains, and the average grain size measured by the maximum dimension of each crystal grain is 1000 mm or less Can be used. For example, Hitachi Metals' nanocrystalline soft magnetic material Finemet (registered trademark) can be used.

  Examples of the magnetic powder used in the present invention include pure iron powder, Fe-Si alloy powder represented by Fe-6.5% Si containing 6 to 7% Si, Fe-Al alloy powder, Fe-Si-Al alloy powder. Fe-Ni alloy powder, Fe-Co alloy powder, amorphous metal magnetic powder, microcrystalline metal magnetic powder, and the like. These may be used alone or in combination as appropriate. In particular, Fe—Si alloy powder containing 6 to 7% of Si is excellent in the respective characteristics of magnetostriction, magnetic core loss, and saturation magnetic flux density Bs, and is a magnetic powder suitable for the present invention. In particular, when the above-described iron-based amorphous soft magnetic material 2605SA1 manufactured by Metglas in the United States is used as a high-permeability magnetic core, the magnetic core is stacked at a filling rate of 80 to 95%, and Si is 6 to By compacting the Fe—Si alloy powder containing 7% at a filling rate of about 70 to 90%, it is possible to achieve a saturation magnetic flux density that is almost the same for both, and a reactor with less loss. From the required reactor characteristics, it is preferable that the maximum relative permeability of the dust core is in the range of 200 or less.

  As the resin used in the present invention, the surface of the magnetic powder is coated so that the powders are insulatively provided with sufficient electric resistance so that the eddy current loss for the AC magnetization of the entire magnetic core does not increase. It also functions as a binder for binding powder. Examples of such a resin include various resins such as an epoxy resin, a polyamide resin, a polyimide resin, a polyester resin, and a silicon resin, and these may be used alone or in appropriate combination.

  As a molding method of the powder magnetic core portion used in the present invention, a casting method in which the mixture of the magnetic powder and the resin is liquefied and then placed in a mold and cured, and injection molding is performed by injection molding into a mold. And a press molding method in which a mixture of a magnetic powder and an organic or inorganic material is filled in a mold and pressed to mold a dust core.

  Since the composite magnetic core of the present invention is composed of a high-permeability magnetic core, a dust core, and a gap, the saturation magnetic flux density as a whole of the magnetic core is high, and the decrease in magnetic permeability with respect to DC superposition is small. Further, by providing the gaps between the high permeability magnetic core portions and between the dust core portions, the fringing magnetic flux is reduced, and the eddy current loss generated in the coil can be reduced. By using this magnetic core, it is possible to realize a reactor having good inductance characteristics, and further having a small size and low loss characteristics.

EXAMPLES The present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
(Example)
One mode of an embodiment of the present invention is shown in FIG. The magnetic core of the reactor of the present invention has an oval shape, and has a major axis of 130 mm, a minor axis of 60 mm, a height of 32 mm, and an average magnetic path length of 280 mm. The high permeability magnetic cores 1, 2, 31 to 34 are laminated bodies prepared by cutting a magnetic core of 82% space factor of an iron-based amorphous magnetic strip (2605SA1 made by Metglas, USA: 25 μm thick). It is. The corner portions 1 and 2 of the semi-annular high permeability magnetic core portion were formed to have a radial thickness of 20.5 mm. The block-shaped high permeability magnetic cores 31 to 34 were formed so that the radial thickness was 20.5 mm and the length in the magnetic path direction was 14 mm. Gaps 21, 28, 29, and 36 were formed between the corner portions 1 and 2 of the high permeability magnetic core portion and the high permeability magnetic core portions 31 to 34, and the width of this gap was 1 mm. The powder magnetic cores 41 to 45 and 51 to 55 are prepared by adding 4 vol% of kaolin and 3 vol% of water glass to Fe-6.5% Si alloy powder having an average particle diameter of 42 μm and forming pressure of 1200 MPa at room temperature. Then, the molded body was heat-treated at a temperature of 1073 K in a nitrogen atmosphere. The dust cores were all the same shape, and had a rectangular parallelepiped shape with a radial thickness of 20.5 mm, a magnetic path length of 11 mm, and a thickness of 32 mm. Further, gaps 22 to 27 and 32 to 37 were formed between the respective powder magnetic cores, and the widths of the gaps were all 1 mm. The magnetic path length ratio between the high permeability magnetic core portion and the dust core portion is 6: 4.
A coil (not shown) is placed on a straight portion including the block-shaped high permeability core portions 31 to 34, the dust core portions 41 to 45 and 51 to 55, and the gaps 21 to 28 and 31 to 38 of the composite core. Provided. The coil was provided so that a flat copper wire having a width of 6 mm and a thickness of 1.6 mm was wound 76 times and all the gaps were covered. Thereby, the reactor of this invention was able to be obtained.
As shown in FIG. 2, this reactor was confirmed to have an inductance of 220 μH or more when the direct current was 160A. Further, it was confirmed that the inductance was 50 μH or more when the direct current was 330 A. This reactor was mounted as L1 of a boost type DC-DC converter having a driving frequency of 10 kHz shown in FIG. 6, and the converter was operated at an input voltage of 200V. Table 1 shows the characteristics when a ripple current having an effective value of 11.5 A is passed at a DC current of 0 A and a frequency of 10 kHz to obtain a voltage of 500 V as a converter output.
The reactor loss was 35 W, and a reactor with very little loss could be obtained.

(Comparative Example 1)
An elliptical composite magnetic core as shown in FIG. 3 was produced. The major axis, minor axis, height, and average magnetic path length are the same dimensions as in Example 1. The corner part is the same laminate as that of Example 1, which was prepared by cutting a magnetic core of 82% space factor of an iron-based amorphous magnetic strip (2605SA1 made by Metglas, USA: 25 μm thick).
Moreover, the straight part was installed so that the blocks 81-84 of the same shape which consist of a laminated body of the said iron-type amorphous magnetic strip may be arrange | positioned between the powder magnetic core parts 41-45, 51-55. The dimensions of the block composed of the dust core and the high permeability core and the width of the gap formed between them are the same as in the first embodiment.
It was confirmed that this reactor had an inductance of 232 μH when the direct current was 160 A, and an inductance of 64 μH when the direct current was 330 A. However, when the reactor loss was measured in the same manner as in Example 1, it was found that a large loss of 46 W was obtained in the reactor in which the high permeability magnetic core portion and the dust core portion were alternately arranged.

(Comparative Example 2)
An elliptical composite magnetic core as shown in FIG. 4 was produced. The major axis, minor axis, height, and average magnetic path length are the same dimensions as in Example 1. The corner part is the same laminate as that of Example 1, which was prepared by cutting a magnetic core of 82% space factor of an iron-based amorphous magnetic strip (2605SA1 made by Metglas, USA: 25 μm thick).
Further, unlike the first embodiment, the straight portion has a structure composed of dust core portions 41 to 47 and 51 to 57 having the same shape. The dimensions of the dust core and the width of the gap formed between them are the same as in Example 1.
It was confirmed that this reactor had an inductance of 222 μH when the direct current was 160 A, and an inductance of 68 μH when the direct current was 330 A. However, when the reactor loss was measured in the same manner as in Example 1, it was found that the reactor loss was as large as 52 W.

(Comparative Example 3)
An elliptical composite magnetic core as shown in FIG. 5 was manufactured. The major axis, minor axis, height, and average magnetic path length are the same dimensions as in Example 1. The corner part is a powder magnetic core part, and using an Fe-6.5% Si alloy powder having an average particle size of 42 μm added with 4 vol% kaolin and 3 vol% water glass, compression molding is performed at a molding pressure of 1200 MPa at room temperature. Thereafter, the molded body was heat-treated at a temperature of 1073 K in a nitrogen atmosphere. The shape and dimensions were manufactured so as to be the same as the corner of the high magnetic permeability part of Example 1.
Moreover, the straight part was comprised only with the block of the laminated body of 82% of the space factor which laminated | stacked the iron-type amorphous magnetic strip (2605SA1 material made from Metglas, USA: thickness 25 micrometers). The dimensions of each block and the width of the gap formed between them are the same as in the first embodiment.
This reactor has an inductance of 222 μH when the direct current is 160 A, which is equivalent to that of the present invention, but is 48 μH when the direct current is 330 A, which is inferior to that of the present invention.

(Comparative Example 4)
As shown in FIG. 6, a magnetic core composed entirely of a high permeability magnetic core was manufactured. The major axis, minor axis, height, and average magnetic path length are the same dimensions as in Example 1. The corner part is the same laminate as that of Example 1, which was prepared by cutting a magnetic core of 82% space factor of an iron-based amorphous magnetic strip (2605SA1 made by Metglas, USA: 25 μm thick).
Also, the block arranged at the straight portion is a laminate produced by cutting an elliptical wound core in the same manner as the corner portion. The width of each block is the same as in the first embodiment. The widths of the gaps formed between them were all 1.5 mm.
It was confirmed that this reactor had an inductance of 222 μH when the direct current was 160 A, and an inductance of 68 μH when the direct current was 330 A. However, when the reactor loss was measured in the same manner as in Example 1, it was found that the reactor loss was as large as 52 W.

It is a figure which shows Example 1 of the composite magnetic core which concerns on this invention. It is a figure which shows the relationship between the electric current and inductance which are applied in the reactor of this invention. It is a figure which shows the conventional magnetic core for reactors. It is a figure which shows the magnetic core for reactors for a comparison. It is a figure which shows the magnetic core for reactors for a comparison. It is a figure which shows the magnetic core for reactors for a comparison. It is a circuit diagram of the boost type DC-DC converter using the reactor which concerns on this invention.

Explanation of symbols

1, 2, 31-34, 61-69, 71-79: high permeability core,
3, 4, 41 to 47, 51 to 57: dust core,
21-28, 31-38: gap,
L1 reactor,
Q1 transistor,
D1 diode,
C1, C2 capacitors

Claims (7)

An annular composite magnetic core,
The composite magnetic core includes first and second linear magnetic paths in which a plurality of magnetic core portions are arranged in a straight line, and first ends arranged on one end side of the first and second linear magnetic paths. 1 corner portion and a second corner portion disposed on the other end side,
The first and second corner portions are formed using a magnetic material having a maximum relative permeability of 500 or more, and are disposed via the first and second linear magnetic paths and a gap,
In the first and second linear magnetic paths, magnetic core portions having high permeability using a magnetic material having a maximum relative permeability of 500 or more are arranged at both ends, respectively, and the maximum relative permeability is provided between the magnetic core portions at both ends. A plurality of magnetic core portions made of a green compact having a magnetic permeability of 200 or less are arranged,
Each of the magnetic core portions arranged in the first and second linear magnetic paths is arranged via a gap, respectively . 2. The composite magnetic core according to claim 1, wherein the first and second corner portions are a laminate of an amorphous soft magnetic strip or a microcrystalline soft magnetic strip. The composite magnetic core according to claim 2, wherein the first and second corner portions are semicircular. 2. The green compact according to claim 1, wherein the green compact is made of iron-silicon alloy powder, iron-silicon-aluminum alloy powder, amorphous soft magnetic powder, or microcrystalline soft magnetic powder. The composite magnetic core according to claim 3. The inductance when measured at a DC current of 160 A and a frequency of 10 kHz is 220 μH or more, and the inductance when measured at a DC current of 330 A and a frequency of 10 kHz is 50 μH or more. Composite magnetic core. 6. The composite magnetic core according to claim 1, wherein a reactor loss is 45 W or less when a ripple current having an effective value of 11.5 A is passed at a frequency of 10 kHz. The composite magnetic core according to any one of claims 1 to 6, wherein the gap between the corner portion and the linear magnetic path and the gap between the magnetic core portions of the linear magnetic path are all covered. A reactor in which a coil is arranged as described above.

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